Studies On The Improvement Of The Strength And Toughness Of Die Casting Low Mg Content Al-Mg Alloy

Although the intensity of casting Al-Mg-Si alloy is moderate,it's still widely used in the Marine propeller manufacturing and automobile manufacturing and other industries because of its excellent corrosion resistance.Due to the requirement of modern material applied to high strength,high toughness,corrosion resistance,resistance to fatigue,room temperature and higher temperature performance.More higher performance Al alloy are developed and applicated.Usually,the performance of alloy materials can be improved by changing the composition and the process to implement.Mixed rare earth is widely used to enhance the performance of alloy as effective inoculant and refine grain agent.Solid solution strengthening and the ageing strengthening can be generated through the formation of supersaturated solid solution or precipitation phase to improve the performance of the alloy.AlMg5Si1 alloy is choosed and poured out of the two groups with different contents of rare earth content for rectangular and circular tensile samples by casting.One group of the poured tensile specimen with different contents of mixed rare earth was solid solution?425?,6h?+?175?,20h?artificial aging treatment.Besides,the original as-cast AlMg5Si1 alloy was proceed by the solid solution treatment in different temperature and holding time.After processing,the alloy was given the tensile test on the ten thousand kilogram of tensile test machine,and measured the hardness of alloy by the use of micro hardness tester.At last SEM was carried out to catch fracture morphology and microstructure.Analyse the relationship between the microstructure and properties of alloy and its influence mechanism using EDS and XRD.The results show that:Rare earth can effectively reduce the size of AlMg5Si1 alloy grain and the secondary dendrite.Rare earths changed the strengthening phase beta?Mg₂Si?morphology,and refinied AlMg5Si1 alloy grain size at the same time,irregular polygon and acicular strengthening phase beta?Mg₂Si?fragmentation of matrix effect is less than the effect of rare earth fine-grain strengthening.AlMg5Si1 alloy tensile strength,vickers hardness and elongation are the best when rare earth content is 0.7%,and rare earth strengthened alloy strong toughness.Single-stage solid solution treatment reached the maximum tensile strength and elongation under the original as-cast AlMg5Si1 alloy at?425?,6h?and?435?,4h?,but alloy hardness decrease after solid solution treatment.The strong toughness of AlMg5Si1 alloy with different contents of rare earth increased significantly after solid solution?425?,6h?+?175?,20h?artificial aging treatment.